Modern tyres are technological marvels. Rubber, both natural and synthetic, is of course by far the most used material, accounting for approximately half a tyre’s weight. But other materials used in the manufacture of tyres include carbon black, silica, oil, sulphur, and steel, to name a few.
More than a large ring of black rubber, a tyre consists of many unseen layers within its rubber casing, and each layer performs specific functions.
In the anatomy of a tyre, we look at its composition and structure.
Each tyre manufacturer chooses materials based on individualised technology, and each component is designed with specific functions in mind while working in conjunction with all the other components. There are three areas of composition:
- Natural rubber – Provides durability and resistance to abrasion.
- Synthetic rubber – Provides heat resistance.
- Carbon black – Increases a rubber’s strength.
- Silica – Delivers better fuel efficiency and grip in the wet.
- Oil – Helps soften rubber.
- Sulphur – Provides elasticity to the rubber.
- Vulcanisation accelerator – Helps build crosslinks between rubber and sulphur for better durability.
- Anti-oxidant – Inhibits the oxidation of rubber.
- Polyester – Used as a reinforcing material for body plies in a passenger tyre, which gives it its strength and resistance to damage.
- Rayon/nylon/Kevlar – Artificial fibres used in passenger tyre body plies.
- Steel wire – Used in a passenger tyre’s beads and steel belts or bands.
Many different components are assembled and moulded together to create one single tyre. The tyre casing consists of all the inner components except the belt.
Tyre layers consist of:
Tread is the outer visible layer of a tyre that has direct contact with the road surface. It makes up approximately one-third of a tyre’s entire weight, provides cushioning, road grip, and water expulsion. Typically made with an abrasion-resistant, higher-grip rubber compound to provide traction and cornering capabilities.
Made from stiff, woven steel cord, the belt lies beneath the tread and provides strength and stability without adding too much weight. It protects the tyre carcass, helps retain the shape as it resists the centrifugal force of a spinning tyre, and increases the tyre’s mileage performance. It also works together with the tyre’s sidewall and tread to traction and cornering capabilities.
3. Body ply
Lying beneath the belt, plies are the skeleton of a tyre and are made from layers of textiles designed to flex without stretching. They add strength and help to optimise directional stability and rolling resistance. Most passenger tyre casings are multi-ply – polyester is commonly used as it adheres well to rubber, and nylon and rayon are also used due to the slightly different benefits they provide.
4. Inner liner
Used as an air seal inside the tyre, this airtight inner tube lies under the body plies and is filled with air when inflated.
The bead is designed to secure the tyre firmly to the wheel. Consisting of a steel loop manufactured from bundles of fine steel wire and coated in bronze or brass and then rubber to resist corrosion, beads are extremely strong.
A special rubber compound is used for the thicker rubber component that covers the tread and the bead. It gives the tyre stability and flexibility and is also designed to be weather resistant as well as resist external damage and abrasion.
While rubber makes up the tread of a tyre and performs many important functions, all the other components serve crucial safety and performance functions. Together, each component and their specific materials properties all work in unison to bring you a product that goes beyond what the eye can see.
Hopefully, this information will go a long way to helping you understand what you’re paying for when buying a new set of passenger tyres!
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